Fuel Cell Heat Pump

ABSTRACT

A heating, ventilation, and air conditioning (HVAC) system includes a fuel cell configured to generate electricity and rejected heat, a hydronic coil, and a circulatory loop configured to selectively circulate a fluid between the fuel cell and the hydronic coil.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

BACKGROUND

Heating, ventilation, and air conditioning systems (HVAC systems) are used in residential and/or commercial areas for heating and/or cooling to create comfortable temperatures inside those areas. These temperature controlled areas may be referred to as comfort zones. Some HVAC systems are heat pump systems. Heat pump systems are generally capable of cooling a comfort zone by operating in a cooling mode for transferring heat from a comfort zone to an ambient zone using a refrigeration cycle (i.e., Rankine cycle). Heat pump systems are also generally capable of reversing the direction of refrigerant flow (i.e., a reverse-Rankine cycle) through the components of the HVAC system so that heat is transferred from the ambient zone to the comfort zone (a heating mode), thereby heating the comfort zone. The efficiency of an HVAC system may be quantified by a coefficient of performance (COP) which is a measure to describe the ratio of useful heat movement to work input.

SUMMARY

In one embodiment, a method of operating an HVAC system is provided that comprises operating a fuel cell to generate electricity and rejected heat, powering a component of the HVAC system using the electricity, and heating air that is handled by the HVAC system using at least a portion of the rejected heat.

In other embodiments, a method of operating an HVAC system is provided that comprises circulating a fluid in a circulatory loop between a fuel cell of the HVAC system and a hydronics coil of the HVAC system, adding heat to the fluid at the fuel cell, and removing heat from the fluid at the hydronics coil.

In yet other embodiments, an HVAC system is provided that comprises a fuel cell configured to generate electricity and rejected heat, a hydronic coil, and a circulatory loop configured to selectively circulate a fluid between the fuel cell and the hydronic coil.

The various characteristics described above, as well as other features, will be readily apparent to those skilled in the art upon reading the following detailed description of the embodiments of the disclosure, and by referring to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and the advantages thereof, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts.

FIG. 1 is a schematic diagram of an HVAC system according to an embodiment of the disclosure;

FIG. 2 is a schematic diagram of the air circulation paths of the HVAC system of FIG. 1;

FIG. 3 is a schematic diagram of an HVAC system comprising a fuel cell according to an embodiment of the disclosure;

FIG. 4 is a flowchart of a method of directing rejected heat from a fuel cell to an HVAC system according to an embodiment of the disclosure;

FIG. 5 is a flowchart of another method of directing rejected heat from a fuel cell to an HVAC system according to an embodiment of the disclosure; and

FIG. 6 is a representation of a general-purpose processor (e.g., electronic controller or computer) system suitable for implementing the embodiments of the disclosure.

DETAILED DESCRIPTION

In a fuel cell, electricity may be generated directly via a conversion of chemical energy to electrical energy. This process of generating electricity may be more efficient, i.e., generate more electricity from the same amount of fuel, compared to electrical generation methods using internal combustion engines. For example, using a fuel cell fueled by natural gas may yield a COP for an HVAC system that exceeds 100% compared to the efficiency obtained by using natural gas furnaces that simply directly burn the fuel to generate heat. Fuel cells may also generate electricity while producing less pollution compared to methods based on electricity generation using internal combustion engines. This disclosure provides systems and methods for operating a fuel cell to efficiently generate electricity for consumption by a heat pump in an HVAC system while also using rejected heat from the fuel cell as an additional heat source for the HVAC system. In some embodiments, a hydronic coil associated with an indoor air handling unit may be utilized.

Referring now to FIG. 1, a simplified schematic diagram of an HVAC system 100 according to an embodiment of this disclosure is shown. HVAC system 100 comprises an indoor unit 102, an outdoor unit 104, and a system controller 106. In some embodiments, the system controller 106 may operate to control operation of the indoor unit 102 and/or the outdoor unit 104. As shown, the HVAC system 100 is a so-called heat pump system that may be selectively operated to implement one or more substantially closed thermodynamic refrigeration cycles to provide a cooling functionality and/or a heating functionality. In this embodiment, the indoor unit 102 further comprises a hydronic coil 182. Further, the HVAC system 100 comprises an electricity generating device 190. A pump 184 may be coupled to the lines connecting the hydronic coil 182 and the electricity generating device 190.

Indoor unit 102 comprises an air handler which comprises an indoor heat exchanger 108 and an indoor fan 110. The air handler is coupled to an indoor metering device 112 and to a hydronic coil 182. Indoor heat exchanger 108 is a plate fin heat exchanger configured to allow heat exchange between refrigerant carried within internal tubing of the indoor heat exchanger 108 and fluids that contact the indoor heat exchanger 108 but that are kept segregated from the refrigerant. In other embodiments, indoor heat exchanger 108 may comprise a spine fin heat exchanger, a microchannel heat exchanger, or any other suitable type of heat exchanger.

The indoor fan 110 is a centrifugal blower comprising a blower housing, a blower impeller at least partially disposed within the blower housing, and a blower motor configured to selectively rotate the blower impeller. In other embodiments, the indoor fan 110 may comprise a mixed-flow fan and/or any other suitable type of fan. The indoor fan 110 is configured as a modulating and/or variable speed fan capable of being operated at many speeds over one or more ranges of speeds. In other embodiments, the indoor fan 110 may be configured a multiple speed fan capable of being operated at a plurality of operating speeds by selectively electrically powering different ones of multiple electromagnetic windings of a motor of the indoor fan 110. In yet other embodiments, the indoor fan 110 may be a single speed fan.

The indoor metering device 112 is an electronically controlled motor driven electronic expansion valve (EEV). In alternative embodiments, the indoor metering device 112 may comprise a thermostatic expansion valve, a capillary tube assembly, and/or any other suitable metering device. The indoor metering device 112 may comprise and/or be associated with a refrigerant check valve and/or refrigerant bypass for use when a direction of refrigerant flow through the indoor metering device 112 is such that the indoor metering device 112 is not intended to meter or otherwise substantially restrict flow of the refrigerant through the indoor metering device 112.

The hydronic coil 182 may comprise a fluid-to-air or an air-to-fluid coil. In an embodiment, the fluid in the hydronic coil 182 is water. In other embodiments, the fluid may comprise a water-glycol solution, steam, or a refrigerant. In some embodiments where the hydronic coil 182 is used for heating, the fluids may comprise hot water and/or steam. In some embodiments where the hydronic coil 182 is used for cooling, the fluids may comprise cooled water and/or refrigerant.

Outdoor unit 104 comprises an outdoor heat exchanger 114, a compressor 116, an outdoor fan 118, an outdoor metering device 120, and a reversing valve 122. Outdoor heat exchanger 114 is a microchannel heat exchanger configured to allow heat exchange between refrigerant carried within internal passages of the outdoor heat exchanger 114 and fluids that contact the outdoor heat exchanger 114 but that are kept segregated from the refrigerant. In other embodiments, outdoor heat exchanger 114 may comprise a spine fin heat exchanger, a plate fin heat exchanger, or any other suitable type of heat exchanger.

The compressor 116 is a multiple speed scroll type compressor configured to selectively pump refrigerant at a plurality of mass flow rates. In alternative embodiments, the compressor 116 may comprise a modulating compressor capable of operation over one or more speed ranges, the compressor 116 may comprise a reciprocating type compressor, the compressor 116 may be a single speed compressor, and/or the compressor 116 may comprise any other suitable refrigerant compressor and/or refrigerant pump.

The outdoor fan 118 is an axial fan comprising a fan blade assembly and fan motor configured to selectively rotate the fan blade assembly. In other embodiments, the outdoor fan 118 may comprise a mixed-flow fan, a centrifugal blower, and/or any other suitable type of fan and/or blower. The outdoor fan 118 is configured as a modulating and/or variable speed fan capable of being operated at many speeds over one or more ranges of speeds. In other embodiments, the outdoor fan 118 may be configured as a multiple speed fan capable of being operated at a plurality of operating speeds by selectively electrically powering different ones of multiple electromagnetic windings of a motor of the outdoor fan 118. In yet other embodiments, the outdoor fan 118 may be a single speed fan.

The outdoor metering device 120 is a thermostatic expansion valve. In alternative embodiments, the outdoor metering device 120 may comprise an electronically controlled motor driven EEV, a capillary tube assembly, and/or any other suitable metering device. The outdoor metering device 120 may comprise and/or be associated with a refrigerant check valve and/or refrigerant bypass for use when a direction of refrigerant flow through the outdoor metering device 120 is such that the outdoor metering device 120 is not intended to meter or otherwise substantially restrict flow of the refrigerant through the outdoor metering device 120.

The reversing valve 122 is a so-called four-way reversing valve. The reversing valve 122 may be selectively controlled to alter a flow path of refrigerant in the HVAC system 100 as described in greater detail below. The reversing valve 122 may comprise an electrical solenoid or other device configured to selectively move a component of the reversing valve 122 between operational positions.

The system controller 106 may comprise a touchscreen interface for displaying information and for receiving user inputs. The system controller 106 may display information related to the operation of the HVAC system 100 and may receive user inputs related to operation of the HVAC system 100. However, the system controller 106 may further be operable to display information and receive user inputs tangentially and/or unrelated to operation of the HVAC system 100. In some embodiments, the system controller 106 may selectively communicate with an indoor controller 124 of the indoor unit 102, with an outdoor controller 126 of the outdoor unit 104, and/or with other components of the HVAC system 100. In some embodiments, the system controller 106 may be configured for selective bidirectional communication over a communication bus 128. In some embodiments, portions of the communication bus 128 may comprise a three-wire connection suitable for communicating messages between the system controller 106 and one or more of the HVAC system 100 components configured for interfacing with the communication bus 128. Still further, the system controller 106 may be configured to selectively communicate with HVAC system 100 components and/or other device 130 via a communication network 132. In some embodiments, the communication network 132 may comprise a telephone network and the other device 130 may comprise a telephone. In some embodiments, the communication network 132 may comprise the Internet and the other device 130 may comprise a so-called smartphone and/or other Internet enabled mobile telecommunication device.

The indoor controller 124 may be carried by the indoor unit 102 and may be configured to receive information inputs, transmit information outputs, and otherwise communicate with the system controller 106, the outdoor controller 126, and/or any other device via the communication bus 128 and/or any other suitable medium of communication. In some embodiments, the indoor controller 124 may be configured to communicate with an indoor personality module 134, receive information related to a speed of the indoor fan 110, transmit a control output to an electric heat relay, transmit information regarding an indoor fan 110 volumetric flow-rate, communicate with and/or otherwise affect control over an air cleaner 136, and communicate with an indoor EEV controller 138. In some embodiments, the indoor controller 124 may be configured to communicate with an indoor fan controller 142 and/or otherwise affect control over operation of the indoor fan 110. In some embodiments, the indoor personality module 134 may comprise information related to the identification and/or operation of the indoor unit 102.

In some embodiments, the indoor EEV controller 138 may be configured to receive information regarding temperatures and pressures of the refrigerant in the indoor unit 102. More specifically, the indoor EEV controller 138 may be configured to receive information regarding temperatures and pressures of refrigerant entering, exiting, and/or within the indoor heat exchanger 108. Further, the indoor EEV controller 138 may be configured to communicate with the indoor metering device 112 and/or otherwise affect control over the indoor metering device 112.

The outdoor controller 126 may be carried by the outdoor unit 104 and may be configured to receive information inputs, transmit information outputs, and otherwise communicate with the system controller 106, the indoor controller 124, and/or any other device via the communication bus 128 and/or any other suitable medium of communication. In some embodiments, the outdoor controller 126 may be configured to communicate with an outdoor personality module 140 that may comprise information related to the identification and/or operation of the outdoor unit 104. In some embodiments, the outdoor controller 126 may be configured to receive information related to an ambient temperature associated with the outdoor unit 104, information related to a temperature of the outdoor heat exchanger 114, and/or information related to refrigerant temperatures and/or pressures of refrigerant entering, exiting, and/or within the outdoor heat exchanger 114 and/or the compressor 116. In some embodiments, the outdoor controller 126 may be configured to transmit information related to monitoring, communicating with, and/or otherwise affecting control over the outdoor fan 118, a compressor sump heater, a solenoid of the reversing valve 122, a relay associated with adjusting and/or monitoring a refrigerant charge of the HVAC system 100, a position of the indoor metering device 112, and/or a position of the outdoor metering device 120. The outdoor controller 126 may further be configured to communicate with a compressor drive controller 144 that is configured to electrically power and/or control the compressor 116.

The HVAC system 100 is shown configured for operating in a so-called heating mode in which heat is absorbed by a refrigerant at the outdoor heat exchanger 114 and heat is rejected by refrigerant at the indoor heat exchanger 108. In some embodiments, the compressor 116 may be operated to compress refrigerant and pump the relatively high temperature and high pressure compressed refrigerant from the compressor 116 to the indoor heat exchanger 108 through the reversing valve 122. From the indoor heat exchanger 108, the refrigerant may be pumped unaffected through the indoor metering device 112 to the outdoor metering device 120 and ultimately to the outdoor heat exchanger 114. The refrigerant may experience a pressure differential across the outdoor metering device 120, be passed through the outdoor heat exchanger 114, and ultimately reenter the compressor 116. As the refrigerant is passed through the outdoor heat exchanger 114, the outdoor fan 118 may be operated to move air into contact with the outdoor heat exchanger 114, thereby transferring heat from the air surrounding the outdoor heat exchanger 114 to the refrigerant. The refrigerant may thereafter re-enter the compressor 116 after passing through the reversing valve 122.

Alternatively, to operate the HVAC system 100 in a so-called cooling mode, most generally, the roles of the indoor heat exchanger 108 and the outdoor heat exchanger 114 are reversed as compared to their operation in the above-described heating mode. For example, the reversing valve 122 may be controlled to alter the flow path of the refrigerant, the indoor metering device 112 may be enabled, and the outdoor metering device 120 may be disabled and/or bypassed. In cooling mode, heat is absorbed by refrigerant at the indoor heat exchanger 108 and heat is rejected by the refrigerant at the outdoor heat exchanger 114. As the refrigerant is passed through the indoor heat exchanger 108, the indoor fan 110 may be operated to move air into contact with the indoor heat exchanger 108, thereby transferring heat to the refrigerant from the air surrounding the indoor heat exchanger 108.

The electricity generating device 190 may supply electricity to the outdoor unit 104. A pump 184 may pump fluid carried in an incoming fluid line from the electricity generating device 190 to the hydronic coil 182, and an outgoing fluid line may carry the fluid from the hydronic coil 182 back to the electricity generating device 190 through the pump 184. In alternative embodiments, the electricity generating device 190 may be an electric generator powered by a fuel source, for example, natural gas. In some embodiments, the electricity generating device 190 may be a fuel cell.

Referring now to FIG. 2, a simplified schematic diagram of the air circulation paths for a structure 200 conditioned by two HVAC systems 100 is shown. In this embodiment, the structure 200 is conceptualized as comprising a lower floor 202 and an upper floor 204. The lower floor 202 comprises zones 206, 208, and 210 while the upper floor 204 comprises zones 212, 214, and 216. The HVAC system 100 associated with the lower floor 202 is configured to circulate and/or condition air of lower zones 206, 208, and 210 while the HVAC system 100 associated with the upper floor 204 is configured to circulate and/or condition air of upper zones 212, 214, and 216.

In addition to the components of HVAC system 100 described above, in this embodiment, each HVAC system 100 further comprises a ventilator 146, a prefilter 148, a humidifier 150, and a bypass duct 152. The ventilator 146 may be operated to selectively exhaust circulating air to the environment and/or introduce environmental air into the circulating air. The prefilter 148 may generally comprise a filter media selected to catch and/or retain relatively large particulate matter prior to air exiting the prefilter 148 and entering the air cleaner 136. The humidifier 150 may be operated to adjust a humidity of the circulating air. The bypass duct 152 may be utilized to regulate air pressures within the ducts that form the circulating air flow paths. In some embodiments, air flow through the bypass duct 152 may be regulated by a bypass damper 154 while air flow delivered to the zones 206, 208, 210, 212, 214, and 216 may be regulated by zone dampers 156. In this embodiment, each indoor unit 102 is shown as comprising a hydronic coil 182.

Still further, each HVAC system 100 may further comprise a zone thermostat 158 and a zone sensor 160. In some embodiments, a zone thermostat 158 may communicate with the system controller 106 and may allow a user to control a temperature, humidity, and/or other environmental setting for the zone in which the zone thermostat 158 is located. Further, the zone thermostat 158 may communicate with the system controller 106 to provide temperature, humidity, and/or other environmental feedback regarding the zone in which the zone thermostat 158 is located. In some embodiments, a zone sensor 160 may communicate with the system controller 106 to provide temperature, humidity, and/or other environmental feedback regarding the zone in which the zone sensor 160 is located.

While HVAC systems 100 are shown as a so-called split system comprising an indoor unit 102 located separately from the outdoor unit 104, alternative embodiments of an HVAC system 100 may comprise a so-called package system in which one or more of the components of the indoor unit 102 and one or more of the components of the outdoor unit 104 are carried together in a common housing or package. The HVAC system 100 is shown as a so-called ducted system where the indoor unit 102 is located remote from the conditioned zones, thereby requiring air ducts to route the circulating air. However, in alternative embodiments, an HVAC system 100 may be configured as a non-ducted system in which the indoor unit 102 and/or multiple indoor units 102 associated with an outdoor unit 104 is located substantially in the space and/or zone to be conditioned by the respective indoor units 102, thereby not requiring air ducts to route the air conditioned by the indoor units 102.

Still referring to FIG. 2, the system controllers 106 may be configured for bidirectional communication with each other and may further be configured so that a user may, using any of the system controllers 106, monitor and/or control any of the HVAC system 100 components regardless of which zones the components may be associated. Further, each system controller 106, each zone thermostat 158, and each zone sensor 160 may comprise a humidity sensor. As such, it will be appreciated that structure 200 is equipped with a plurality of humidity sensors in a plurality of different locations. In some embodiments, a user may effectively select which of the plurality of humidity sensors is used to control operation of one or more of the HVAC systems 100.

Referring now to FIG. 3, a simplified schematic diagram of an HVAC system 300 comprising a fuel cell 310 according to an embodiment of the disclosure is shown. The HVAC system 300 comprises the fuel cell 310 that comprises a heat exchanger 312, a domestic water heater 320 comprising a heat exchanger 322, the outdoor unit 104 and the indoor unit 102 comprising the hydronic coil 182. The HVAC system 300 further comprises a circulation loop 330 which circulates a fluid, for example water, between the heat exchanger 312, the domestic water heater 320 and the hydronic coil 182. Although FIG. 3 illustrates an embodiment wherein the circulated fluid is water, it is to be understood that other fluids may be used.

The loop 330 may comprise a plurality of pipes which may be made of made of a variety of materials, e.g., polyvinyl chloride (PVC/uPVC), ductile iron, steel, cast iron, polypropylene, polyethylene, or copper. In some embodiments, the loop 330 may comprise a thermostat to measure a temperature of the circulated fluid. In some embodiments, the loop 330 may also comprise a plurality of valves that may open and close in response to an external stimulus, e.g., a difference between a measured fluid temperature and a fluid temperature setpoint. For example, after raising a temperature setpoint of the domestic water heater 320, valves in the loop 330 connecting the domestic water heater 320 and the fuel cell 310 may open to allow the water to flow to the domestic heater 320. Opening the valves may promote thermal exchange between water circulated in the domestic water heater 320 and the water circulated in the loop 330. On the other hand, when the temperature of the circulated water drops below the existing water heater 320 setpoint temperature, the valves may close. In embodiments where a valve may be closed to prevent circulation of fluid through the heat exchanger 322, additional bypass fluid conduits and/or valves may be provided to allow fluid to bypass the water heater 320 and to circulate through the hydronic coil 182. The loop 330 may be in contact with the domestic water heater 320 to heat up water, based on measurements of the temperature vs. a specified setpoint. The heat exchanger 322 may be configured to allow heat exchange between water heated by the domestic water heater 320 and water heated by the fuel cell 310.

The fuel cell 310 may be supplied by a fuel to generate electricity that may be used to power a component of the outdoor unit 104. For example, the electricity may power a compressor, an outside unit, an inside unit, and/or any other portion of an HVAC system. While FIG. 3 shows an embodiment with a fuel cell, in other embodiments, the fuel cell 310 may be replaced with another energy generating source such as an engine, electricity generator etc. In an embodiment, this heat pump is an air-to-air heat pump. The electricity generated by the fuel cell 310 may be based on a chemical reaction between the fuel and an oxidant. A variety of combinations of fuels and oxidants may be used. Examples of fuels are natural gas, hydrogen, hydrocarbons and alcohols. Air, oxygen, chlorine and chlorine dioxide may serve as oxidants. In an embodiment, the fuel supplied to the fuel cell 310 may be natural gas, and the oxidant may be air.

The rejected heat from the fuel cell 310 may be utilized for an HVAC system functionality to increase the efficiency of the HVAC system 300. For example, the rejected heat may be directed to the indoor unit 102 for heating a space to which the indoor unit 102 supplies air. Another use for the rejected heat may be radiant floor heating. In an embodiment, the rejected heat may be used to heat the fluid that is exchanged between the fuel cell 310 and the hydronic coil 182. In some embodiments, the rejected heat from the fuel cell 310 may be directed to the domestic water heater 320 to heat water of the domestic water heater 320. In some embodiments, the rejected heat from the fuel cell 310 may be transported in water which is selectively circulated between the fuel cell 310, the hydronic coil 182 and/or the domestic water heater 320.

The domestic water heater 320 may circulate water through the heat exchanger 322 located in a domestic water tank. In an embodiment, the domestic water heater 320 may be a conventional storage heater comprising a tank. During operation, when the hot water tap is turned on, the domestic water heater 320 may release hot water from the top of the tank. Cold water may then enter the bottom of the tank, to replace that hot water and ensure that the tank is full. In another embodiment, the domestic water heater 320 may be a so-called demand, or instantaneous, water heater to which hot water from the fuel cell 310 may be routed on demand, when needed. In yet another embodiment, the domestic water heater 320 may be a solar water heater that may receive hot water from the fuel cell 310 as an additional source of heated water.

The efficiency of the heat-pump based HVAC system 300 operating in a heating mode may exceed the efficiency of a furnace that simply burns natural gas, propane, or other fuels for the purpose of simply distributing the resultant heat of combustion. For example, in some cases, a furnace configured to combust natural gas may comprise an efficiency of about 80% to about 95% which translates to a COP of about 0.80 to about 0.95, respectively, with the furnace efficiency generally not being sensitive to outdoor ambient temperature. Comparatively, in determining an efficiency of an HVAC system 300 comprising both a heat pump and an electrical power generation source (i.e. fuel cell 310), the efficiencies of the electrical power generation source with regard to electrical power generation efficiency and heat generation efficiency must be considered as well as the efficiency of the vapor compression cycle efficiency of the heat pump itself (with the heat pump operating at about 47 degrees Fahrenheit ambient outdoor temperature). In some cases, the electrical power generation source may comprise an electricity generation COP in a range of about 0.2 to about 0.4 while also comprising a heat generation COP in a range of about 0.6 to 0.4 (with a total additive COP of about 0.8) while the vapor compression cycle of the heat pump powered by the generated electricity may comprise a COP in a range of about 3.0 to about 4.0. Accordingly, such an HVAC system 300, in some less efficient embodiments, may comprise an overall system COP of about 1.2 (i.e. 0.2*3+0.6=1.2), which is greater than the COP of the above-described natural gas furnace alone. In more efficient embodiments, an HVAC system 300 may comprise an overall system COP of about 2.0 (i.e. 0.4*4.0+0.4=2.0), which is much more efficient than the above-described natural gas furnace alone.

The hydronic heating capability of the HVAC system 300 may replace the need for use of so-called “emergency heat” or “auxiliary heat” sources such as electrical resistance heating elements with the heat pump when the heating capacity of the heat pump itself is insufficient to meet a heating demand. Additionally, during warmer seasons or environmental conditions, the fuel cell 310 could be used to power the heat pump in cooling mode thereby providing an opportunity to reduce peak electrical demand and avoid high peak electrical rates. The fuel cell 310 may also be configured to operate during electrical grid power outages to provide electricity for heating, cooling, and/or other purpose that comprises powering electrical loads.

Referring now to FIG. 4, a flow chart of a method 400 of directing rejected heat from a fuel cell to at least one of a domestic water heater and a hydronic coil is shown. In some embodiments, the HVAC system 300 may be operated according to method 400. The method may begin at block 410 where rejected heat from a fuel cell is directed to a heat exchanger of the fuel cell. For example, the rejected heat may be directed from the fuel cell 310 to the heat exchanger 312. Once heat is transferred to the heat exchanger of the fuel cell, the method may progress to block 420. At block 420, heat may be transferred from the heat exchanger of the fuel cell to a fluid within the heat exchanger of the fuel cell. In some cases, the fluid may be fluid carried in a circulatory loop such as the loop 330. In some embodiments, the fluid may be water that passes through the heat exchanger 312 and resultantly receives at least a portion of the rejected heat to increase a temperature of the water and/or to generate steam. Once at least a portion of the rejected heat is successfully transferred to the fluid of the heat exchanger of the fuel cell, at block 430, the fluid may be transported to at least one of a domestic water heater and a hydronic coil. For example, the fluid may be directed to the domestic water heater 320 and/or the fluid may be directed to the hydronic coil 182.

Next, at block 440, heat may be transferred from the fluid to at least one of the domestic water heater and the hydronic coil. For example, heat may be transferred to the domestic water heater via a heat exchanger, such as the heat exchanger 322, to be used for heating water that is circulated in the domestic water heater 320. Alternatively and/or additionally, the heat may be transferred to a hydronic coil such as the hydronic coil 182 to ultimately heat air used for heating a space conditioned by an HVAC system 300. At block 450, after transferring at least some heat from the fluid to at least one of the domestic water heater and the hydronic coil, the fluid may be circulated via a circulatory loop such as loop 330 back to the heat exchanger 322 of the fuel cell. This method may be run continuously or may be re-executed or re-started at periodic intervals.

Referring now to FIG. 5, a flow chart of a method 500 of directing rejected heat from a fuel cell to at least one of a domestic water heater, a hydronic coil, and the atmosphere is shown. In some embodiments, an HVAC system 300 may be operated according to method 500. The method may begin at block 510 where rejected heat from a fuel cell is directed to a heat exchanger of the fuel cell. For example, the rejected heat may be directed from the fuel cell 310 to the heat exchanger 312. Once heat is transferred to the heat exchanger of the fuel cell, the method may progress to block 520. At block 520, heat may be transferred from the heat exchanger of the fuel cell to a fluid within the heat exchanger of the fuel cell. In some cases, the fluid may be fluid carried in a circulatory loop such as the loop 330. In some embodiments, the fluid may be water that passes through the heat exchanger 312 and resultantly receives at least a portion of the rejected heat to increase a temperature of the water and/or to generate steam.

Next, at block 530, the method 500 may determine whether to direct the heated fluid to a domestic water heater. In some embodiments, the method 500 may determine whether to direct the heated fluid to a domestic water heater based on a comparison between a water temperature setpoint of the water heater and a temperature of the fluid that has received the rejected heat. For example, in some embodiments, if the water temperature setpoint of the water heater is set at a value of 120 degrees Fahrenheit and the temperature of the fluid that has received the rejected heat is less than 120 degrees Fahrenheit, the method 500 may determine at block 530 that the fluid should not be directed to the water heater because flowing the fluid to the water heater may reduce a temperature of the potable water within the water heater. After selectively directing (at block 540) or not directing fluid to the water heater, the method 500 may direct the fluid to a hydronic coil at block 550. In deciding whether to direct the fluid to the hydronic coil, a determination may be made as to whether a space being conditioned by the HVAC system may benefit from an increase in heating supplied to the space, in some embodiments, via the use of a temperature setpoint of the space being compared to a temperature of the fluid. Accordingly, in some embodiments, heat may be transferred from the fluid to the hydronic coil at block 560 if the temperature setpoint of the space is lower than the temperature of the fluid.

Next, the method 500 may determine at block 570 whether rejected heat should be dumped to the atmosphere. In some embodiments, the fluid may have an associated maximum temperature setpoint that the fluid should not exceed. Accordingly, in some embodiments, after selectively supplying the fluid to the domestic water heater and the hydronic coil, the fluid temperature may be determined at block 570. In some embodiments, if the fluid temperature is above the maximum temperature setpoint, actions may be taken to dump the rejected heat to the atmosphere. In some embodiments, a fan and/or blower associated with the fluid may be operated to cause heat transfer from the fluid to the atmosphere and/or any other suitable heat sink. Heat may be dumped to the atmosphere at block 580 and the fluid may thereafter return to the heat exchanger of the fuel cell at block 590 in a manner substantially similar to block 450 of FIG. 4. In some embodiments, the maximum temperature setpoint may be set as a temperature selected to prevent damage to the associated fluid conduits, prevent undesirably fast changes in temperatures of either the hot water heater or hydronic coil, and/or to prevent undesirable heat buildup in the fuel cell itself.

In alternative embodiments of HVAC systems, heated water may be selectively injected into and/or mixed with potable water of domestic hot water heaters. In embodiments where water may be removed from a circulatory loop to enter into a hot water heater, the circulatory loop may further be attached to a water source that may replace removed water. Further, in alternative embodiments, any suitable combination of bypass fluid conduits and/or fluid valves may be incorporated to selectively route fluid to the domestic water heater, hydronic coil, and/or any other suitable device that may benefit from fluid heated by rejected heat of a fuel cell. In other embodiments, fluid may be selectively circulated to a hydronic coil in response to a comparison between a temperature setpoint and a temperature of the fluid being selectively circulated. For example, in some embodiments, fluid that is cooler than a desired room temperature may be prevented from being circulated through a hydronic coil while the HVAC system comprising the hydronic coil is performing a heating operation to meet a heating demand.

FIG. 6 illustrates a typical, general-purpose processor (e.g., electronic controller or computer) system 1300 that includes a processing component 1310 suitable for implementing one or more embodiments disclosed herein. In addition to the processor 1310 (which may be referred to as a central processor unit or CPU), the system 1300 might include network connectivity devices 1320, random access memory (RAM) 1330, read only memory (ROM) 1340, secondary storage 1350, and input/output (I/O) devices 1360. In some cases, some of these components may not be present or may be combined in various combinations with one another or with other components not shown. These components might be located in a single physical entity or in more than one physical entity. Any actions described herein as being taken by the processor 1310 might be taken by the processor 1310 alone or by the processor 1310 in conjunction with one or more components shown or not shown in the drawing.

The processor 1310 executes instructions, codes, computer programs, or scripts that it might access from the network connectivity devices 1320, RAM 1330, ROM 1340, or secondary storage 1350 (which might include various disk-based systems such as hard disk, floppy disk, optical disk, or other drive). While only one processor 1310 is shown, multiple processors may be present. Thus, while instructions may be discussed as being executed by a processor, the instructions may be executed simultaneously, serially, or otherwise by one or multiple processors. The processor 1310 may be implemented as one or more CPU chips.

The network connectivity devices 1320 may take the form of modems, modem banks, Ethernet devices, universal serial bus (USB) interface devices, serial interfaces, token ring devices, fiber distributed data interface (FDDI) devices, wireless local area network (WLAN) devices, radio transceiver devices such as code division multiple access (CDMA) devices, global system for mobile communications (GSM) radio transceiver devices, worldwide interoperability for microwave access (WiMAX) devices, and/or other well-known devices for connecting to networks. These network connectivity devices 1320 may enable the processor 1310 to communicate with the Internet or one or more telecommunications networks or other networks from which the processor 1310 might receive information or to which the processor 1310 might output information.

The network connectivity devices 1320 might also include one or more transceiver components 1325 capable of transmitting and/or receiving data wirelessly in the form of electromagnetic waves, such as radio frequency signals or microwave frequency signals. Alternatively, the data may propagate in or on the surface of electrical conductors, in coaxial cables, in waveguides, in optical media such as optical fiber, or in other media. The transceiver component 1325 might include separate receiving and transmitting units or a single transceiver. Information transmitted or received by the transceiver 1325 may include data that has been processed by the processor 1310 or instructions that are to be executed by processor 1310. Such information may be received from and outputted to a network in the form, for example, of a computer data baseband signal or signal embodied in a carrier wave. The data may be ordered according to different sequences as may be desirable for either processing or generating the data or transmitting or receiving the data. The baseband signal, the signal embedded in the carrier wave, or other types of signals currently used or hereafter developed may be referred to as the transmission medium and may be generated according to several methods well known to one skilled in the art.

The RAM 1330 might be used to store volatile data and perhaps to store instructions that are executed by the processor 1310. The ROM 1340 is a non-volatile memory device that typically has a smaller memory capacity than the memory capacity of the secondary storage 1350. ROM 1340 might be used to store instructions and perhaps data that are read during execution of the instructions. Access to both RAM 1330 and ROM 1340 is typically faster than to secondary storage 1350. The secondary storage 1350 is typically comprised of one or more disk drives or tape drives and might be used for non-volatile storage of data or as an over-flow data storage device if RAM 1330 is not large enough to hold all working data. Secondary storage 1350 may be used to store programs or instructions that are loaded into RAM 1330 when such programs are selected for execution or information is needed.

The I/O devices 1360 may include liquid crystal displays (LCDs), touch screen displays, keyboards, keypads, switches, dials, mice, track balls, voice recognizers, card readers, paper tape readers, printers, video monitors, transducers, sensors, or other well-known input or output devices. Also, the transceiver 1325 might be considered to be a component of the I/O devices 1360 instead of or in addition to being a component of the network connectivity devices 1320. Some or all of the I/O devices 1360 may be substantially similar to various components disclosed herein.

At least one embodiment is disclosed and variations, combinations, and/or modifications of the embodiment(s) and/or features of the embodiment(s) made by a person having ordinary skill in the art are within the scope of the disclosure. Alternative embodiments that result from combining, integrating, and/or omitting features of the embodiment(s) are also within the scope of the disclosure. Where numerical ranges or limitations are expressly stated, such express ranges or limitations should be understood to include iterative ranges or limitations of like magnitude falling within the expressly stated ranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4, etc.; greater than 0.10 includes 0.11, 0.12, 0.13, etc.). For example, whenever a numerical range with a lower limit, RI, and an upper limit, Ru, is disclosed, any number falling within the range is specifically disclosed. In particular, the following numbers within the range are specifically disclosed: R=RI+k* (Ru−RI), wherein k is a variable ranging from 1 percent to 100 percent with a 1 percent increment, i.e., k is 1 percent, 2 percent, 3 percent, 4 percent, 5 percent, . . . 50 percent, 51 percent, 52 percent, . . . , 95 percent, 96 percent, 97 percent, 98 percent, 99 percent, or 100 percent. Moreover, any numerical range defined by two R numbers as defined in the above is also specifically disclosed. Use of the term “optionally” with respect to any element of a claim means that the element is required, or alternatively, the element is not required, both alternatives being within the scope of the claim. Use of broader terms such as comprises, includes, and having should be understood to provide support for narrower terms such as consisting of, consisting essentially of, and comprised substantially of. Accordingly, the scope of protection is not limited by the description set out above but is defined by the claims that follow, that scope including all equivalents of the subject matter of the claims. Each and every claim is incorporated as further disclosure into the specification and the claims are embodiment(s) of the present invention. 

1. A method of operating a heating, ventilation, and air conditioning (HVAC) system, comprising: operating a fuel cell to generate electricity and rejected heat; powering a component of the HVAC system using the electricity; and heating air that is handled by the HVAC system using at least a portion of the rejected heat.
 2. The method of claim 1, wherein the electricity powers a compressor of the HVAC system.
 3. The method according to claim 1, further comprising: directing at least a portion of the rejected heat to a hydronics coil of the HVAC system.
 4. The method according to claim 1, further comprising: directing at least a portion of the rejected heat to a domestic water heater.
 5. The method according to claim 1, further comprising: directing at least a portion of the rejected heat to at least one of a hydronics coil of the HVAC system and a domestic water heater via a circulatory loop.
 6. The method according to claim 1, further comprising: directing at least a portion of the rejected heat to at least one of a hydronics coil of the HVAC system and a domestic water heater in response to a comparison between a fluid temperature setpoint and a temperature of a fluid receiving the rejected heat.
 7. A method of operating a heating, ventilation, and air conditioning (HVAC) system, comprising: circulating a fluid in a circulatory loop between a fuel cell of the HVAC system and a hydronics coil of the HVAC system; adding heat to the fluid at the fuel cell; removing heat from the fluid at the hydronics coil.
 8. The method according to claim 7, further comprising: electrically powering at least a portion of the HVAC system using electrical energy generated by the fuel cell.
 9. The method according to claim 8, wherein a compressor of the HVAC system is powered using the electrical energy generated by the fuel cell.
 10. The method according to claim 7, further comprising: circulating the fluid to a domestic water heater.
 11. The method according to claim 7, wherein the fluid comprises water.
 12. The method according to claim 7, further comprising selectively circulating the fluid in response to a comparison between a temperature setpoint and a temperature of the fluid.
 13. The method according to claim 7, further comprising: selectively mixing the fluid with potable water of a domestic water heater.
 14. A heating, ventilation, and air conditioning (HVAC) system, comprising: a fuel cell configured to generate electricity and rejected heat; a hydronic coil; and a circulatory loop configured to selectively circulate a fluid between the fuel cell and the hydronic coil.
 15. The HVAC system according to claim 14, wherein the fuel cell comprises a heat exchanger associated with the circulatory loop.
 16. The HVAC system according to claim 14, wherein the fuel cell is configured to consume natural gas.
 17. The HVAC system according to claim 14, wherein the circulatory loop is configured to selectively circulate the fluid through a heat exchanger of a domestic water heater.
 18. The HVAC system according to claim 17, wherein the HVAC system is configured to circulate the fluid to at least one of the hydronic coil and the domestic water heater in response to a comparison between a temperature setpoint and a temperature of the fluid.
 19. The HVAC system according to claim 14, wherein at least a portion of the electricity generated by the fuel cell powers a compressor of the HVAC system.
 20. The HVAC system according to claim 14, wherein the fuel cell is configured to consume propane. 